1. Field of the Invention
This invention relates to cleaning apparatus for removing toner from dielectric members of copiers.
2. Description of the Prior Art
Modern high-speed electrographic copiers make document reproductions by exposing an electrically-charged dielectric member to a light image of the document. The light image selectively discharges the dielectric member to form a latent image charge pattern corresponding to the document. An oppositely charged developer material is brought into contact with the latent image to develop the image. The developed image is then transferred to a receiver sheet and fixed to the sheet by heat and/or pressure to yield the desired copy.
The developer material includes a resinous powder known as toner. If the toner is not completely transferred to the receiver sheet, the residual toner may scatter throughout the copier and contaminate other components within the copier. It is, therefore, standard practice to include apparatus for cleaning the dielectric member immediately after the image is transferred from the dielectric member to the receiver sheet.
A typical cleaning apparatus for a dielectric member is shown in commonly assigned U.S. Pat. No. 4,459,012, which issued on July 10, 1984 to J. D. Allen et al. Briefly, a rotating bristle brush sweeps residual toner from a photoconductive dielectric member. A source of vacuum establishes an air flow which transports toner from the brush to filter apparatus.
Because the surface of a dielectric member is relatively soft and easily abraded, extreme care must be taken to not harm the surface. While brushes and other surface-contacting means of suitably soft material are generally effective to remove residual toner, they do require a great frequency of maintenance, have the potential for creating an undesirable dust condition, and can malfunction to the extent of abrading the surface of the dielectric member.
Various techniques have been tried in order to overcome the disadvantages associated with brush cleaning. One such attempt is shown in U.S. Defensive Publication Pat. No. T 893,001, which was published on Dec. 14, 1971, in the name of J. D. Fisler. In the Fisler disclosure, toner is removed from the photoconductive dielectric member by contact with a fluid medium through which ultrasonic energy is transmitted. Although cleaning by such means may be effective and is achieved without adversely affecting the dielectric member, the location of the cleaning station is restricted to those regions around the dielectric member where the cleaning fluid can drain directly from the dielectric member into a sump for filtration and recirculation. For example, U.S. Pat. No. 3,483,034, which issued Dec. 9, 1969 to D. Ensminger, shows a fluid photoconductive dielectric member cleaning station at the bottom of the dielectric member. However, in many electrographic copier configurations, positioning the cleaning station at such a region would be inconvenient.
Dielectric member cleaning using a fluid has been proposed at positions other than at the bottom of the dielectric member, such as shown in U.S. Pat. No. 4,165,172, which issued on Aug. 21, 1979 to T. Okamoto et al. In such applications, the cleaning fluid is prevented from running down the dielectric member by a blade member in contact with the surface of the dielectric member. However, the blade negates the advantages of the fluid cleaning insofar as prevention of the risk of abrading the surface of the dielectric member is concerned.